Phase shift and phase shift assisted sensing

ABSTRACT

Disclosed is a phase measurement system and method. Multiple frequency orthogonal signals are transmitted simultaneously along the same row conductor. One of the signals may be low frequency signal. The other signal may be a high frequency signal. The field of the low frequency signal may extend further above a touch surface than the high frequency signal. The phase data from the low frequency signal may be used to provide information about a touch event.

This application includes material which is subject to copyrightprotection. The copyright owner has no objection to the facsimilereproduction by anyone of the patent disclosure, as it appears in thePatent and Trademark Office files or records, but otherwise reserves allcopyright rights whatsoever.

FIELD

The disclosed systems relate in general to the field of user input, andin particular to devices sensitive to touch, including, hover andpressure.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features, and advantages of thedisclosure will be apparent from the following more particulardescription of embodiments as illustrated in the accompanying drawings,in which reference characters refer to the same parts throughout thevarious views. The drawings are not necessarily to scale, emphasisinstead being placed upon illustrating principles of the disclosedembodiments.

FIG. 1 is a high level block diagram illustrating an embodiment of alow-latency touch sensor device.

FIG. 2 is a high level block diagram illustrating another embodiment ofa low-latency touch sensor device.

FIG. 3 is a functional block diagram illustrating an embodiment offrame-phase synchronization.

FIG. 4 is a graph illustrating an exemplary result of a touch event.

FIG. 5 is a graph showing an exemplary displacement vector from theexemplary result of a touch event shown in FIG. 4.

DETAILED DESCRIPTION

This application relates to user interfaces such as found in U.S. patentapplication Ser. No. 15/195,675, entitled “Frame-Phase Synchronizationin Frequency Division Modulated Touch Systems.” The entire disclosure ofthat application, and the applications incorporated therein byreference, are incorporated herein by reference. Familiarity with theconcepts and terms therein is presumed.

An embodiment of the disclosure is an apparatus having a plurality ofantenna mounted on a substrate. The apparatus has signal generatorconductively connected to each of at least a first group of theplurality of antenna, the signal generator is adapted to generate aplurality of distinct signals during a plurality of sequentialintegration periods. The apparatus has a signal receiver conductivelyconnected to each of at least a second group of the plurality ofantennas, the signal receiver adapted to take a sequence of digitalsamples of signals on each of at least a second antenna group during theplurality of sequential integration periods. The apparatus has a signalprocessing system operatively connected to the signal receiver, thesignal processing system being adapted to; perform a discrete Fouriertransform on each sequence of digital samples taken during each of theplurality of sequential integration periods; determine a phase anglecorresponding to each of the plurality of distinct signals in eachsequence of digital samples for each of the plurality of sequentialintegration periods; and utilize the phase angle of at least one of theplurality of distinct signals to identify a touch event.

An embodiment of the disclosure is a method having the steps ofgenerating a plurality of distinct signals on at least a first group ofa plurality of antenna during a plurality of sequential integrationperiods; taking a sequence of digital samples of signals received oneach of at least a second antenna group of the plurality of antennasduring the plurality of sequential integration periods; performing adiscrete Fourier transform on each sequence of digital samples takenduring each of the plurality of sequential integration periods;determining a phase angle corresponding to each of the plurality ofdistinct signals in each sequence of digital samples for each of theplurality of sequential integration periods; and utilizing the phaseangle of at least one of the plurality of distinct signals to identify atouch event.

In various embodiments, the present disclosure is directed to systems(e.g., objects, panels or keyboards) sensitive to hover, contact andpressure and their applications in real-world, artificial reality,virtual reality and augmented reality settings. It will be understood byone of ordinary skill in the art that the disclosures herein applygenerally to all types of systems using fast multi-touch to detecthover, contact an pressure. In an embodiment, the present system andmethod can be applied to keyboards, including but not limited tomembrane keyboards, dome-switch keyboards, scissor-switch keyboards,capacitive keyboards, mechanical-switch keyboards, buckling-springkeyboards, hall-effect keyboards, laser projection keyboard, roll-upkeyboards, and optical keyboard technology.

Throughout this disclosure, the terms “touch”, “touches”, “contact”,“contacts”, “hover”, or “hovers” or other descriptors may be used todescribe events or periods of time in which a user's finger, a stylus,an object, or a body part is detected by a sensor. In some sensors,detections occur only when the user is in physical contact with asensor, or a device in which it is embodied. In some embodiments, and asgenerally denoted by the word “contact”, these detections occur as aresult of physical contact with a sensor, or a device in which it isembodied. In other embodiments, and as sometimes generally referred toby the term “hover”, the sensor may be tuned to allow for the detectionof “touches” that are hovering at a distance above the touch surface orotherwise separated from the sensor device and causes a recognizablechange, despite the fact that the conductive or capacitive object, e.g.,a finger, is not in actual physical contact with the surface. Therefore,the use of language within this description that implies reliance uponsensed physical contact should not be taken to mean that the techniquesdescribed apply only to those embodiments; indeed, nearly all, if notall, of what is described herein would apply equally to “contact” and“hover”, each of which being a “touch”. Generally, as used herein, theword “hover” refers to non-contact touch events or touch, and as usedherein the term “hover” is one type of “touch” in the sense that “touch”is intended herein. Thus, as used herein, the phrase “touch event” andthe word “touch” when used as a noun include a near touch and a neartouch event, or any other gesture that can be identified using a sensor.“Pressure” refers to the force per unit area exerted by a user contact(e.g., presses their fingers or hand) against the surface of an object.The amount of “pressure” is similarly a measure of “contact”, i.e.,“touch”. “Touch” refers to the states of “hover”, “contact”, “pressure”,or “grip”, whereas a lack of “touch” is generally identified by signalsbeing below a threshold for accurate measurement by the sensor. Inaccordance with an embodiment, touch events may be detected, processed,and supplied to downstream computational processes with very lowlatency, e.g., on the order of ten milliseconds or less, or on the orderof less than one millisecond.

As used herein, and especially within the claims, ordinal terms such asfirst and second are not intended, in and of themselves, to implysequence, time or uniqueness, but rather, are used to distinguish oneclaimed construct from another. In some uses where the context dictates,these terms may imply that the first and second are unique. For example,where an event occurs at a first time, and another event occurs at asecond time, there is no intended implication that the first time occursbefore the second time, after the second time or simultaneously with thesecond time. However, where the further limitation that the second timeis after the first time is presented in the claim, the context wouldrequire reading the first time and the second time to be unique times.Similarly, where the context so dictates or permits, ordinal terms areintended to be broadly construed so that the two identified claimconstructs can be of the same characteristic or of differentcharacteristic. Thus, for example, a first and a second frequency,absent further limitation, could be the same frequency, e.g., the firstfrequency being 10 Mhz and the second frequency being 10 Mhz; or couldbe different frequencies, e.g., the first frequency being 10 Mhz and thesecond frequency being 11 Mhz. Context may dictate otherwise, forexample, where a first and a second frequency are further limited tobeing frequency-orthogonal to each other, in which case, they could notbe the same frequency.

The presently disclosed systems and methods provide for designing,manufacturing and using capacitive touch sensors, and particularlycapacitive touch sensors that employ a multiplexing scheme based onorthogonal signaling such as but not limited to frequency-divisionmultiplexing (FDM), code-division multiplexing (CDM), or a hybridmodulation technique that combines both FDM and CDM methods. Referencesto frequency herein could also refer to other orthogonal signal bases.As such, this application incorporates by reference Applicants' priorU.S. patent application Ser. No. 13/841,436, filed on Mar. 15, 2013entitled “Low-Latency Touch Sensitive Device” and U.S. patentapplication Ser. No. 14/069,609 filed on Nov. 1, 2013 entitled “FastMulti-Touch Post Processing.” These applications contemplate FDM, CDM,or FDM/CDM hybrid touch sensors which may be used in connection with thepresently disclosed sensors. In such sensors, touches are sensed when asignal from a row is coupled (increased) or decoupled (decreased) to acolumn and the result received on that column.

This application employs principles used in fast multi-touch sensors andother interfaces disclosed in the following U.S. Pat. Nos. 9,019,224 B2,9,811,214 B2, 9,804,721 B2, 9,710,113 B2, 9,158,411 B2, and thefollowing U.S. patent applications: Ser. Nos. 14/466,624, 15/162,240,15/690,234, 15/195,675, 15/200,642, 15/821,677, 62/540,458, 62/575,005,62/619,656 and PCT publication PCT/US2017/050547, familiarity with thedisclosure, concepts and nomenclature therein is presumed. The entiredisclosure of those application and the applications incorporatedtherein by reference are incorporated herein by reference. Details ofthe presently disclosed system and method for performing phase measureare then described further below under the heading “Phase Measurement.”

As used herein, the phrase “touch event” and the word “touch” when usedas a noun include a near touch and a near touch event, or any othergesture that can be identified using a sensor. In accordance with anembodiment, touch events may be detected, processed and supplied todownstream computational processes with very low latency, e.g., on theorder of ten milliseconds or less, or on the order of less than onemillisecond.

In an embodiment, a fast multi-touch sensor utilizes a projectedcapacitive method that has been enhanced for high update rate and lowlatency measurements of touch events. The technique can use parallelhardware and higher frequency waveforms to gain the above advantages.Also disclosed are methods to make sensitive and robust measurements,which methods may be used on transparent display surfaces and which maypermit economical manufacturing of products which employ the technique.In this regard, a “capacitive object” as used herein could be a finger,other part of the human body, a stylus, or any object to which thesensor is sensitive. The sensors and methods disclosed herein need notrely on capacitance. With respect to, e.g., the optical sensor, suchembodiments utilize photon tunneling and leaking to sense a touch event,and a “capacitive object” as used herein includes any object, such as astylus or finger, that that is compatible with such sensing. Similarly,“touch locations” and “touch sensitive device” as used herein do notrequire actual touching contact between a capacitive object and thedisclosed sensor.

FIG. 1 illustrates certain principles of a fast multi-touch sensor 100in accordance with an embodiment. At reference no. 200, a differentsignal is transmitted into each of the surface's rows. The signals aredesigned to be “orthogonal”, i.e., separable and distinguishable fromeach other. At reference no. 300, a receiver is attached to each column.The receiver is designed to receive any of the transmitted signals, oran arbitrary combination of them, with or without other signals and/ornoise, and to individually determine a measure, e.g., a quantity foreach of the orthogonal transmitted signals present on that column. Thetouch surface 400 of the sensor comprises a series of rows and columns(not all shown), along which the orthogonal signals can propagate. In anembodiment, the rows and columns are designed so that, when they are notsubject to a touch event, a lower or negligible amount of signal iscoupled between them, whereas, when they are subject to a touch event, ahigher or non-negligible amount of signal is coupled between them. In anembodiment, the opposite could hold—having the lesser amount of signalrepresent a touch event, and the greater amount of signal represent alack of touch. Because the touch sensor ultimately detects touch due toa change in the coupling, it is not of specific importance, except forreasons that may otherwise be apparent to a particular embodiment,whether the touch-related coupling causes an increase in amount of rowsignal present on the column or a decrease in the amount of row signalpresent on the column. As discussed above, the touch, or touch eventdoes not require a physical touching, but rather an event that affectsthe level of coupled signal.

With continued reference to FIG. 1, in an embodiment, generally, thecapacitive result of a touch event in the proximity of both a row andcolumn may cause a non-negligible change in the amount of signal presenton the row to be coupled to the column. More generally, touch eventscause, and thus correspond to, the received signals on the columns.Because the signals on the rows are orthogonal, multiple row signals canbe coupled to a column and distinguished by the receiver. Likewise, thesignals on each row can be coupled to multiple columns. For each columncoupled to a given row (and regardless of whether the coupling causes anincrease or decrease in the row signal to be present on the column), thesignals found on the column contain information that will indicate whichrows are being touched simultaneously with that column. The quantity ofeach signal received is generally related to the amount of couplingbetween the column and the row carrying the corresponding signal, andthus, may indicate a distance of the touching object to the surface, anarea of the surface covered by the touch and/or the pressure of thetouch.

When a row and column are touched simultaneously, some of the signalthat is present on the row is coupled into the corresponding column (thecoupling may cause an increase or decrease of the row signal on thecolumn). (As discussed above, the term touch or touched does not requireactual physical contact, but rather, relative proximity.) Indeed, invarious implementations of a touch device, physical contact with therows and/or columns is unlikely as there may be a protective barrierbetween the rows and/or columns and the finger or other object of touch.Moreover, generally, the rows and columns themselves are not in touchwith each other, but rather, placed in a proximity that allows an amountof signal to be coupled there-between, and that amount changes(positively or negatively) with touch. Generally, the row-columncoupling results not from actual contact between them, nor by actualcontact from the finger or other object of touch, but rather, by thecapacitive effect of bringing the finger (or other object) into closeproximity—which close proximity resulting in capacitive effect isreferred to herein as touch.

The nature of the rows and columns is arbitrary and the particularorientation is irrelevant. Indeed, the terms row and column are notintended to refer to a square grid, but rather to a set of conductorsupon which signal is transmitted (rows) and a set of conductors ontowhich signal may be coupled (columns). (The notion that signals aretransmitted on rows and received on columns itself is arbitrary, andsignals could as easily be transmitted on conductors arbitrarilydesignated columns and received on conductors arbitrarily named rows, orboth could arbitrarily be named something else.) Further, it is notnecessary that the rows and columns be in a grid. Other shapes arepossible as long as a touch event will touch part of a “row” and part ofa “column”, and cause some form of coupling. For example, the “rows”could be in concentric circles and the “columns” could be spokesradiating out from the center. And neither the “rows” nor the “columns”need to follow any geometric or spatial pattern, thus, for example, thekeys on keyboard could be arbitrarily connected to form rows and columns(related or unrelated to their relative positions.) Moreover, it is notnecessary for there to be only two types signal propagation channels:instead of rows and columns, in an embodiment, channels “A”, “B” and “C”may be provided, where signals transmitted on “A” could be received on“B” and “C”, or, in an embodiment, signals transmitted on “A” and “B”could be received on “C”. It is also possible that the signalpropagation channels can alternate function, sometimes supportingtransmitters and sometimes supporting receivers. It is also contemplatedthat the signal propagation channels can simultaneously supporttransmitters and receivers—provided that the signals transmitted areorthogonal, and thus separable, from the signals received. Three or moretypes of antenna conductors may be used rather than just “rows” and“columns.” Many alternative embodiments are possible and will beapparent to a person of skill in the art after considering thisdisclosure.

As noted above, in an embodiment the touch surface 400 comprises aseries of rows and columns, along which signals can propagate. Asdiscussed above, the rows and columns are designed so that, when theyare not being touched, one amount of signal is coupled between them, andwhen they are being touched, another amount of signal is coupled betweenthem. The change in signal coupled between them may be generallyproportional or inversely proportional (although not necessarilylinearly proportional) to the touch such that touch is less of a yes-noquestion, and more of a gradation, permitting distinction between moretouch (i.e., closer or firmer) and less touch (i.e., farther orsofter)—and even no touch. Moreover, a different signal is transmittedinto each of the rows. In an embodiment, each of these different signalsare orthogonal (i.e., separable and distinguishable) from one another.When a row and column are touched simultaneously, signal that is presenton the row is coupled (positively or negatively), causing more or lessto appear in the corresponding column. The quantity of the signal thatis coupled onto a column may be related to the proximity, pressure orarea of touch.

At reference 300 receiver is attached to each column. The receiver isdesigned to receive the signals present on the columns, including any ofthe orthogonal signals, or an arbitrary combination of the orthogonalsignals, and any noise or other signals present. Generally, the receiveris designed to receive a frame of signals present on the columns, and toidentify the columns providing signal. In an embodiment, the receiver(or a signal processor associated with the receiver data) may determinea measure associated with the quantity of each of the orthogonaltransmitted signals present on that column during the time the frame ofsignals was captured. In this manner, in addition to identifying therows in touch with each column, the receiver can provide additional(e.g., qualitative) information concerning the touch. In general, touchevents may correspond (or inversely correspond) to the received signalson the columns. For each column, the different signals received thereonindicate which of the corresponding rows is being touched simultaneouslywith that column. In an embodiment, the amount of coupling between thecorresponding row and column may indicate e.g., the area of the surfacecovered by the touch, the pressure of the touch, etc. In an embodiment,a change in coupling over time between the corresponding row and columnindicates a change in touch at the intersection of the two.

Turning to FIG. 2, a sensor 205 is shown. In an embodiment, sensor 205comprises a plurality of antenna 230, 235 spaced apart from one-anotheron a substrate 225. While two rows of antennas 230, 235 are shown, asillustrated by the ellipses, in an embodiment, only one row is required,however two or more rows may be used. Similarly, while each rowcomprises 12 antennas, fewer or more antennas may be used in a row. Inan embodiment, the antenna are each between 1 mm and 5 mm in height (asviewed on the page), and between 3 mm and 25 mm in width (as viewed onthe page). In an embodiment, each antenna is 2×5 mm. In an embodiment,each antenna is 2×8 mm. In an embodiment, each antenna is 3×5 mm. In anembodiment, each antenna is 2×8 mm. In an embodiment, each antenna is2×10 mm. In an embodiment, each antenna is 3×10 mm. In an embodiment,each antenna is 4×10 mm. It will be apparent to a person of skill in theart that the antenna can be sized and shaped as appropriate for theapplication.

The antennas are spaced from one-another. In an embodiment, each antennais at least 1 mm away from every other antenna. In an embodiment, eachantenna is at least 2 mm away from every other antenna. In anembodiment, each antenna is at least 3 mm away from every other antenna.In an embodiment, each antenna is at least 4 mm away from every otherantenna. In an embodiment, each antenna is at least 5 mm away from everyother antenna. In an embodiment, the antenna spacing varies amongantenna such that some antenna are closer together than others. It willbe apparent to a person of skill in the art that the antenna can bespaced from one-another as appropriate for the application.

In an embodiment, antennas are distributed on a substrate for use with akeyboard. In an embodiment, antennas of 2×8 mm are spaced fromone-another by 3 mm along their long dimension sides, and by 4 mm alongthe short dimension sides, and are laid out on a substrate 225 that issufficient in size to be placed beneath the keys of a keyboard (i.e.,about 15×40 mm). Although the antennas may be aligned with the keys of akeyboard, it is not necessary to align the antennas with the keys. In anembodiment (as illustrated), the antennas are not aligned with the keysof a keyboard. It will be apparent to a person of skill in the art thatthe antenna can be dimensioned and spaced from one-another asappropriate for another keyboard or for another application.

In an embodiment, the plurality of antenna 230, 235 which may be used astransmit antenna 230 and a plurality of receive antenna 235, althoughthe designations of transmit and receive are arbitrary, and can bereversed by swapping the antenna's connecting from transmitter toreceiver or vice versa. In an embodiment, a matrix switcher (not shown)could be used to dynamically reconfigure the connection of an antennafrom a receiver to a transmitter. In an embodiment, an antenna can beconnected to both a transmitter and receiver, which transmitter could beused simultaneously, or at different times.

In an embodiment, signal generator 260 and transmitter 240 areoperatively connected to each of a plurality of transmit antennas 230and configured to generate and transmit each of a plurality offrequency-orthogonal signals 260 to each of the plurality of transmitantenna 230. In an embodiment, a receiver 280 and signal processor 270are associated with each receive antenna 325 and operatively connectedthereto.

In an embodiment, a mixed signal integrated circuit 210 comprises signalgenerator 250, transmitter 240, receiver 280 and signal processor 270.In an embodiment, the mixed signal integrated circuit 210 is adapted togenerate one or more signals and send the signals to transmit antennas230. In an embodiment, the mixed signal integrated circuit 210 isadapted to generate a plurality of frequency-orthogonal signals 260 andsend the plurality of frequency-orthogonal signals 260 to the transmitantenna 230. In an embodiment, the mixed signal integrated circuit 210is adapted to generate a plurality of frequency-orthogonal signals 260and send one or more of the plurality of frequency-orthogonal signals260 to each of a plurality of transmit antenna 230. In an embodiment,the frequency-orthogonal signals are in the range from DC up to about2.5 GHz. In an embodiment, the frequency-orthogonal signals are in therange from DC up to about 1.6 MHz. In an embodiment, thefrequency-orthogonal signals are in the range from 50 KHz to 200 KHz.The frequency spacing between the frequency-orthogonal signals should begreater than or equal to the reciprocal of an integration period (i.e.,the sampling period).

In an embodiment, the signal processor 270 of mixed signal integratedcircuit 210 (or a downstream component or software) is adapted todetermine at least one value representing each frequency orthogonalsignal transmitted to a transmit antenna 230. In an embodiment, thesignal processor 270 of mixed signal integrated circuit 210 (or adownstream component or software) performs a Fourier transform toreceived signals. In an embodiment, the mixed signal integrated circuit210 is adapted to digitize received signals. In an embodiment, the mixedsignal integrated circuit 210 (or a downstream component or software) isadapted to digitize received signals and perform a discrete Fouriertransform (DFT) on the digitized information. In an embodiment, themixed signal integrated circuit 210 (or a downstream component orsoftware) is adapted to digitize received signals and perform a FastFourier transform (FFT) on the digitized information—an FFT being onetype of discrete Fourier transform.

It will be apparent to a person of skill in the art in view of thisdisclosure that a DFT, in essence, treats the sequence of digitalsamples (e.g., window) taken during a sampling period (e.g., integrationperiod) as though it repeats. As a consequence, signals that are notcenter frequencies (i.e., not integer multiples of the reciprocal of theintegration period (which reciprocal defines the minimum frequencyspacing)), may have relatively nominal, but unintended consequence ofcontributing small values into other DFT bins. Thus, it will also beapparent to a person of skill in the art in view of this disclosurethat, the term orthogonal as used herein is not “violated” by such smallcontributions. In other words, as we use the term frequency orthogonalherein, two signals are considered frequency orthogonal if substantiallyall of the contribution of one signal to the DFT bins is made todifferent DFT bins than substantially all of the contribution of theother signal.

In an embodiment, received signals are sampled at at least 1 MHz. In anembodiment, received signals are sampled at at least 2 MHz. In anembodiment, received signals are sampled at 4 Mhz. In an embodiment,received signals are sampled at 4.096 Mhz. In an embodiment, receivedsignals are sampled at more than 4 MHz.

To achieve kHz sampling, for example, 4096 samples may be taken at 4.096MHz. In such an embodiment, the integration period is 1 millisecond,which per the constraint that the frequency spacing should be greaterthan or equal to the reciprocal of the integration period provides aminimum frequency spacing of 1 KHz. (It will be apparent to one of skillin the art in view of this disclosure that taking 4096 samples at e.g.,4 MHz would yield an integration period slightly longer than amillisecond, and not achieving kHz sampling, and a minimum frequencyspacing of 976.5625 Hz.) In an embodiment, the frequency spacing isequal to the reciprocal of the integration period. In such anembodiment, the maximum frequency of a frequency-orthogonal signal rangeshould be less than 2 MHz. In such an embodiment, the practical maximumfrequency of a frequency-orthogonal signal range should be less thanabout 40% of the sampling rate, or about 1.6 MHz. In an embodiment, aDFT (which could be an FFT) is used to transform the digitized receivedsignals into bins of information, each reflecting the frequency of afrequency-orthogonal signal transmitted which may have been transmittedby the transmit antenna 130. In an embodiment 2048 bins correspond tofrequencies from 1 KHz to about 2 MHz. It will be apparent to a personof skill in the art in view of this disclosure that these examples aresimply that, exemplary. Depending on the needs of a system, and subjectto the constraints described above, the sample rate may be increased ordecrease, the integration period may be adjusted, the frequency rangemay be adjusted, etc.

In an embodiment, a DFT (which could be an FFT) output comprises a binfor each frequency-orthogonal signal that is transmitted. In anembodiment, each DFT (which could be an FFT) bin comprises an in-phase(I) and quadrature (Q) component. In an embodiment, the sum of thesquares of the I and Q components is used as measure corresponding tosignal strength for that bin. In an embodiment, the square root of thesum of the squares of the I and Q components is used as measurecorresponding to signal strength for that bin. It will be apparent to aperson of skill in the art in view of this disclosure that a measurecorresponding to the signal strength for a bin could be used as ameasure related to touch. In other words, the measure corresponding tosignal strength in a given bin would change as a result of a touch eventin proximity to a tixel.

As used herein, the term tixel (a/k/a taxel) refers to the intersectionof interaction between any transmitting conductor or antenna and anyreceiving conductor or antenna. In a grid layout, the term tixel canrefer to the interactions occurring at the crossing point (when viewedin plan) between the rows and columns. In receive and transmit antennalayouts, the term tixel can refer to the interactions occurring betweenany transmit antenna and any receive antenna. For example, in aconfiguration with three antennas laid out TX1, RX1, TX2 or RX1, TX1,TX2, depending on the proximity of the antenna, a tixel may existbetween the RX1 antenna and each TX antenna. Thus, in an embodiment, ineither configuration, a touch event can affect both the RX1-TX1 tixeland the RX1-TX2 tixel. Where antenna are set out in a grid (e.g., 3×3)(or in more dimensions) tixels can exist—again, depending on layout andproximity—between each TX and each RX antenna. In an embodiment, a 3×3grid has 4 TX and 5 RX antennas, and may have as many as 20 tixels. Inan embodiment, a 3×3×3 cube of antennas comprising, e.g., 9 TX and 18 RXantennas, may have as many as 162 tixels.

Referring back to the above-mentioned illustrative example having a4.096 MHz sampling rate, a 1 millisecond integration period and afrequency spacing of 1 kHz, an FFT (or other DFT) will result in 2048bins providing I and Q components for each of the frequencies from 1 kHzto over 2 MHz. In an embodiment, only center frequencies integermultiples of the minimum frequency spacing (which is the reciprocal ofthe integration period)—are used. In an embodiment, frequencies may beused that, although orthogonal to the other frequencies being used, arenot center frequencies. For example, using the above illustrativeexample, the frequencies 50.1 kHz and 50.5 kHz are not centerfrequencies because they are not integer multiples of the minimumfrequency spacing. Frequencies that are not integer multiples of theminimum frequency spacing shall be referred to herein as off-centerfrequencies or OCFs.

In an embodiment, FFT-processed receiver data (or e.g., DFT-processedreceiver data) comprising OCFs will fall into two adjacent bins. In anembodiment, the amount of an OCF that will fall into each of the twoadjacent bins is proportional to how much the OCF is off center. As anillustration, assume that a 100 kHz center frequency is transmitted, andafter the DFT (which could be an FFT) is performed, the bincorresponding to the 100 kHz frequency contained I and Q components of1.0 and 0.0, respectively. Assuming there is frame-phase alignment, thesame result occurs each time if the tixel remains unaffected by touch ornoise. In an subsequent frame, assume that instead of transmitting the100 kHz center frequency, a 100.5 kHz off-center frequency istransmitted, and in an illustrative embodiment, after the FFT isperformed, the bin corresponding to the 100 kHz frequency contained Iand Q components of about 0.71 and 0.0, respectively and the bincorresponding to the 101 kHz frequency contained I and Q components ofabout 0.71 and 0.0, respectively. This results because the amplitudevalues reflecting the off-center frequency were split between the twoadjacent bins, and square root of the sum of their squares must equal 1,the amplitude of the signal as it was received for the purpose of thisillustration as a center frequency. The amplitudes are also affected bythe sinc-squared nature of the Fourier transform frequency-domainwindow, but we are neglecting that effect for the purposes of thisillustration. In an subsequent frame, assume that instead oftransmitting the 100.5 kHz off-center frequency, a 100.25 kHz off-centerfrequency is transmitted, and in an illustrative embodiment, after theFFT is performed, the bin corresponding to the 100 kHz frequencycontained I and Q components of about 0.87 and 0.0, respectively and thebin corresponding to the 101 kHz frequency contained I and Q componentsof about 0.5 and 0.0, respectively. Again, the result occurs because thevalues reflecting the off-center frequency were split between the twoadjacent bins. In practice, the values do not split as evenly as thisexemplary and simplified illustration, however, it will be apparent toone of skill in the art in view of this disclosure, that the energy ofthe transmitted frequency will be split into and represented by twobins, and that the I and Q values represent the in-phase and quadratureamplitudes of that energy.

In an embodiment, off-center frequencies are elected for use as a checkagainst noise. Consider the illustration above using 100.5 kHz, havinghalf of its power showing up in the bin corresponding to 100 kHz andhalf of its power showing up in the bin corresponding to 101 kHz. In anembodiment, unequal amounts in either bin could be disregarded as noise.This principle would hold for any off-center frequency providing a firstproportion of its energy into one bin and a second proportion of itsenergy into a second bin.

In an embodiment, two off-center frequencies are sent per transmitconductor or antenna. In an embodiment, two off-center orthogonalfrequencies are sent per transmit conductor or antenna, and the twooff-center orthogonal frequencies are each a known proportionoff-center, e.g., the frequency is 20%, 50% or 75% of the way from onecenter frequency to the next. In an embodiment, two off-centerorthogonal frequencies are sent per transmit conductor or antenna, andthe two off-center orthogonal frequencies each are a known proportionoff-center, and the resulting power distribution between each of the twooff-center orthogonal frequencies and their corresponding bins is known.In an embodiment, two off-center orthogonal frequencies are sent pertransmit conductor or antenna and thus four bins are used per tixel. Inan embodiment, a high frequency off-center signal and a low frequencyoff-center signal are sent to a transmit conductor or antenna, whichresults in two low-frequency bins and two-high frequency bins being usedper tixel. In an embodiment, the off-center frequencies or signals areorthogonal to each other.

In an embodiment, the frequency of a signal is dithered to achieve aparticular aspect, and thus a particular distribution of its power intoadjacent bins. In an embodiment, the frequency of a signal is ditheredwith a code to achieve a particular aspect, and thus a particulardistribution of its power into adjacent bins. In an embodiment, thefrequency of a signal is dithered with a pseudo-random code to achieve aparticular aspect.

Frame-Phase Synchronization

As discussed above, in an embodiment, each of a plurality offrequency-orthogonal signals are operatively driven onto a group ofconductors or antennas, and a signals may be received during anintegration period (e.g., a sampling period) from the same group ofconductors or antennas or from another group of conductors or antennas.It will be apparent to one of skill in the art in view of thisdisclosure that, over time, a constantly generated plurality offrequency-orthogonal signals will have a repeating sequence, and maycause beats. As described in more detail below, starting thetransmission of a plurality of frequency-orthogonal signals where eachsignal has a known initial phase alignment will make the location of thebeat or beats predictable. Moreover, restarting the transmission of aplurality of frequency-orthogonal signals where each signal has a knowninitial phase alignment before each integration period may prevent anundesirable beat or beats from being sampled.

In an embodiment, signal emitters are correlated with the receivers on asensor and the receiver initiates its integration period (e.g., asampling period) at a known time with respect to the sequence of thetransmitted data, thus, the data collected can be correlated with thetransmission of the emitted signals.

The methods and systems provided herein are used to overcome certainconditions in which noise or other artifacts produce interference with,jitter in, or phantom touches on, the FMT sensor. FMT method may beimplemented by driving multiple frequencies simultaneously. The receiverthen processes a combined waveform of that may have varying degrees ofthe multiple frequencies to calculate values for each of the individualdriving frequencies e.g., with the use of a DFT (which could be an FFT).Frame-to-frame variation in phase offsets of the driving signals, andthus in the signal supplied to the DFT (which could be an FFT) maycreate a difference in the resulting calculated values, therebyaffecting the accuracy of the FMT sensor.

The present embodiments provide methods and systems for reducing oreliminating undesirable results by mitigating the variation in thecalculated values for each of the individual frequencies when the touchdevice is in the same state of touch. By way of example, in anembodiment, prior to beginning each frame, the signal can besynchronized by resetting all of the emitted signal frequencies to apredetermined, or known, initial phase. Such resetting may be repeatedprior to acquisition of all subsequent frames. In an embodiment, thereceiver can be set (or triggered) to capture a frame at successiveperiods when the emitted signal frequencies are known to be in aparticular phase and phase relationship. Because the emitted signalfrequencies have a beat period, in an embodiment, a frame period (i.e.,the reciprocal of the frame frequency) is selected as a multiple of thebeat period, thus ensuring that the samples from each frame will be inthe same phase and phase relationship as the previous frame.

Several approaches are illustrated below to mitigate the variation incalculated values for the individual frequencies. Generally, each of theapproaches endeavors to make the repeating capture operations, which toexploit the claimed touch detector are captured one after another (butnot necessarily one immediately after another), capture frames of datathat are identical in phase. In other words, the captured data isframe-phase synchronized between frames. In various embodiments, thiscan be accomplished by reinitiating transmission of the signal, at aknown initial phase, at a known time before capture. As used herein,“known initial phase” means that the initial phase is predetermined orthe phase is generated at the time of the initial transmission and itbecomes known in subsequent frames. In various embodiments, this can beaccomplished by continuously transmitting, but determining when frameswill be frame-phase synchronized and delaying capture until theframe-phase synchronization. The several embodiments below illustrate avariety of systems and methods for frame-phase synchronization, but arenot intended to limit the scope of the claims. Other systems and methodsof frame-phase synchronization to improve touch data will becomeapparent to persons of skill in the art in view of this disclosure, andare thus included within the scope of this disclosure.

A method for synchronizing one or more simultaneously transmittedsignals on a touch detector may involve one or more of the processingoperations as described below. In an embodiment, the touch detectorcomprises a matrix comprising “N” rows and “M” columns of conductivematerial, the touch detector is arranged such that the paths of each ofthe “N” rows in the matrix crosses the path of each of the “M” columnsin the matrix. In an embodiment, the touch detector comprises a receiverassociated with each of the “M” columns and at least one signalprocessor. (In an embodiment, instead of the rows and columns, the touchdetector comprises a plurality of antenna as illustrated in FIG. 2, andthe touch detector comprises a receiver associated with each of thereceive antenna and a signal processor). The transmission of signals isinitiated on each of the rows (or transmit antennas) of the matrix. Inan embodiment, transmission is achieved by supplying signal-relatedvalues to a DAC that is connected to the rows (or transmit antennas).The transmitted signals are frequency-orthogonal to each other, and thetransmitted signals each have a specific initial phase. At apredetermined time after the signal transmission is initiated, a frameof data is captured for each of the columns of the matrix (or receiveantennas), the frames of data captured represents the signals present onthe corresponding column (or receive antennas) during the frame capturetime. In an embodiment, the frame of data is captured by sampling thecolumns (or receive antennas) using an ADC. These steps of initiatingtransmission, waiting and capturing frames is repeated, providing map ofdata that show changes in time associated with touch, but mitigatingphase-related artifacts that could show up as noise or changing touchdata. It will hereafter be apparent to one of skill in the art in viewof this disclosure that the use of antennas or conductors (e.g.,row/column), for these purposes, can be interchangeable.

A basic one-row, one-column touch detector apparatus is described toillustrate some of the principles discussed above. A row conductor and acolumn conductor are arranged such that the path of the row conductorcrosses the path of the column conductor. A clock having a predeterminedperiodicity is provided. A signal emitter is adapted to initiatetransmission of a signal at each of a plurality of intervals on theclock starting at a first time. Each time the transmission of the signalis initiated, the signal has the same initial phase as that signal hadwhen transmissions of that signal was previously initiated. A receiveris adapted to start receiving a frame of data on the column at each ofthe plurality of intervals starting at a second, later time. And asignal processor is adapted to determine one of a range of measures ofthe signal present within the received frame, the one measure beingreflective of touch.

The following illustrative embodiment discloses a touch detectorapparatus having multiple rows and/or columns. A matrix of “N” rows and“M” columns of conductive material is arranged so that the paths of eachof the rows in the matrix crosses the path of each of the columns. Theillustrative touch detector also has a clock having a predeterminedperiodicity. Signal emitters are used to transmit unique signals on toeach of the rows. The transmission is initiated at each of a pluralityof intervals on the clock starting at a first time. In an embodiment,each of the transmitted signals is orthogonal to each of the othertransmitted signals. In this illustrative embodiment, each of thetransmitted signals has a known or predetermined initial phase—namely aphase that is the same each time its transmission is initiated. Areceiver, receives a frame on each of the columns at each intervalstarting at a later time, that is, a time after transmission isinitiated. The delay between transmission initiation and receivingallows signal propagation to normalize in the matrix, overcoming e.g.,inertia. A signal processor is used to determine one of a range ofmeasures for each of the transmitted signals, reflecting a value forpresence of the transmitted signal within the received frame. In anembodiment, the signal processor and the receiver may be part of thesame component. In another embodiment, the signal processor and thereceiver are not part of the same component.

An illustrative embodiment of a method for determining measurementsrelated to touch on a touch detector is also provided and shown in FIG.3. In this method, a touch detector has a matrix comprising “N” rows and“M” columns of conductive material. The touch detector is arranged suchthat the paths of each of the “N” rows in the matrix cross the paths ofeach of the “M” columns in the matrix. The touch detector further havinga receiver associated with at least one of the “M” columns, and at leastone signal processor. The method including repeatedly: (i) initiating atransmission of a row signals at a known phase 600; (ii) waiting for therow signals to normalize in the matrix (e.g., to charge the matrix) 601;and (iii) receiving frames of data from columns 602. A measure of rowsignals found in the frames may be determined as shown in step 603. Inan embodiment, an amount of row signal found on a column may bedetermined using an FFT function on the frame. In an embodiment, the FFTfunction will include both in-phase (I) and quadrature (Q) componentsrepresenting an amount of row signal. While noise and other artifactsmay also be found on the column, touch from a touch detector is intendedto be the predominant cause of the FFT measure. In an embodiment, thesum of the squares of the I and Q components is used as measurecorresponding to a signal strength. In an embodiment, the square root ofthe sum of the squares of the I and Q components is used as measurecorresponding to signal strength. In an embodiment, the measures may beused to produce a heat map corresponding to touch (e.g., signalstrength) as shown in step 604.

Another illustrative method for determining measurements related totouch on a touch detector comprising a matrix of rows and columns ofconductive material. The illustrative touch detector comprises areceiver associated with at least one of the columns. The methodconsists of repeatedly: (i) initiating a transmission of signals, eachof the signals being transmitted on respective ones of the rows of thematrix, each of the signals being frequency-orthogonal to each of theother signals, and each of the signals being at a known initial phase;(ii) waiting a predetermined period of time after initiating thetransmission, the predetermined period of time being at least sufficientfor the signals to charge the matrix; and (iii) receiving on thereceiver a frame of signals present on each of the columns of the matrixduring a second predetermined period of time, the step of receivingbeginning immediately after the predetermined period of time. The knowninitial phase for each of the signals may be predetermined, or if notpredetermined, may be repeated as the method is repeatedly carried out,and may be the same as, or differ from the known initial phase of eachother of the signals. In this way, each frame captured should havesimilar alignment of the phase of each respective signal. Once thecapture is complete, the frames may be processed to determine a measureof the frequency-orthogonal signals present on the columns when it wascaptured. In an embodiment, the measure may be made by taking an FFT ofthe frame. Changes in the FFT values from one frame to the next arereflective of touch.

Another illustrative embodiment of an apparatus for measuring a level ofa transmitted signal on a touch detector is also described using a touchdetector having a first and second row conductor and a column conductor,arranged such that the path of each of the first and second rowconductors cross the path of the column conductor. Signal emitters areadapted to transmit orthogonal signals on row conductors, respectively.A receiver receives a frame on the column at an interval related to thebeat frequency of the orthogonal signals. A signal processor may be usedto determine a measure of each of the signals present within thereceived frame—and thus, the capacitive response of the touch detector.In an embodiment, the signal processor and the receiver are part of thesame component. In another embodiment, the signal processor and thereceiver are not part of the same component. In an embodiment, theinterval is a multiple of the beat frequency of the orthogonal signals.

Yet another illustrative apparatus for measuring a level of a pluralityof orthogonal signals in a touch detector is also described using atouch detector having a matrix comprising rows and columns of conductivematerial, arranged such that the path of the matrix of rows and columnscross. A plurality of signal emitters each adapted to transmit one of aplurality of orthogonal signals onto a row of the matrix, each of theplurality of orthogonal signals being orthogonal to each of the other ofthe plurality of orthogonal signals, and the plurality of orthogonalsignals having a beat frequency. The beat frequency has a periodic beat.A receiver starts receiving a frame on one of the columns of the matrixat a time related to the periodic beat of the beat frequency. A signalprocessor adapted to determine a measure of each of the plurality oforthogonal signals present within the received frame. In an embodiment,the signal processor and the receiver are part of the same component. Inan embodiment, the signal processor and the receiver are not part of thesame component. In an embodiment, the receiver receives a frame,periodically, at an interval related to the beat frequency of theplurality of orthogonal signals.

A further illustrative apparatus for measuring a level of a transmittedsignal on a touch detector includes a first row conductor, and a firstcolumn conductor, arranged such that the path of the first row conductorcrosses the path of the first column conductor. A clock having apredetermined periodicity is present. A first signal emitter adapted toinitiate a plurality of temporally separate transmissions of a signal,each transmission of a signal starting at a time according to the clock,and the signal having a known initial phase. A receiver, adapted toreceive a frame from a column, the frame comprising at least a portionof one of the plurality of temporally separate transmissions. Thereceiver adapted to start receiving the frame from the column at a latertime according to the clock, the later time on the clock being after thecorresponding transmission starting time. A signal processor adapted todetermine a measure of the first signal present within each receivedframe. In an embodiment, this measure may be made by an FFT of the framefor the column conductor. In an embodiment, the measure may include bothin-phase and quadrature components. In an embodiment, the signalprocessor and the receiver are part of the same component. In anotherembodiment, the signal processor and the receiver are not part of thesame component.

Yet a further illustrative apparatus for measuring a level oftransmitted signals on a touch detector includes a matrix comprisingrows and columns arranged such that the path of each of the rows crossesthe path of each of the columns. A clock having a predeterminedperiodicity is present. Signal emitters adapted to initiate a pluralityof transmissions at different times. Each of the plurality oftransmissions starting at a different time according to the clock. Eachof the plurality of transmissions comprising a plurality of orthogonalsignals. Each of the signal emitters transmitting a unique one of theplurality of orthogonal signals on a unique one of the rows during eachof the plurality of transmissions occurring at different times. Each ofthe plurality of orthogonal signals has the same initial phase. Areceiver adapted to receive a frame from each of the columns, each ofthe frames comprising at least a portion of one of the plurality oftransmissions, and adapted to start receiving the frame from the columnat a later time according to the clock. This later time on the clockbeing after the corresponding transmission starting time. And a signalprocessor adapted to determine a measure of each of the plurality oforthogonal signals present within each of the received frames. In anembodiment, the measures may be made by an FFT of the frame for thecolumns. In an embodiment, the measures may include both in-phase (I)and quadrature (Q) components. In an embodiment, the sum of the squaresof the I and Q components is used as measure corresponding to signalstrength. In an embodiment, the square root of the sum of the squares ofthe I and Q components is used as measure corresponding to signalstrength. In an embodiment, the signal processor and the receiver arepart of the same component. In another embodiment, the signal processorand the receiver are not part of the same component.

Phase Measurement

As discussed far above, it has been understood for several years that ameasure corresponding to signal strength in a given bin (e.g., (I²+Q²)or (I²+Q²)^(1/2)) changes as a result of a touch event proximate to atixel. Because the square-root function is computationally expensive,the former (I²+Q²) is often a preferred measurement. Attention has notbeen focused on phase shift occurring as a consequence of touch, likelybecause in an uncorrelated system, the phases of the signals receivedtend to be random from frame to frame. The recent development of theabove-described frame-phase synchronization was directed to overcomingcertain conditions in which noise or other artifacts produceinterference with, jitter in, or phantom touches on an FMT sensor.Nonetheless, according to the reference, frame-phase synchronization wasused in an effort to better measure the signal strength. Synchronizationof the phase from frame to frame, however, led to the discovery thattouch events affect the phase of signals, and thus, touch events can bedetected by examining changes in the phase corresponding to a receivedfrequency (e.g., a bin). Thus, in addition to the received signalstrength, the received signal phase also informs detection. In anembodiment, phase changes are used to detect touch events. In anembodiment, a combination of changes in signal strength and changes inphase are used to detect touch events. In an embodiment, a touch delta(a vector representing a change of phase and the change in signalstrength of the received signal) is calculated. In an embodiment, touchevents are detected by examining the change in a touch delta over time.

The implementation of frame-phase synchronization provides anopportunity for obtaining another potential source of data that can beused for detecting, identifying and/or measuring a touch event. At leastsome of the noise that affects the measurement of the signal strengthmay not affect the measurement of phase. Thus, this phase measurementmay be used instead of, or in combination with a signal strengthmeasurement to detect, identify and/or measure a touch event. For theavoidance of doubt, it is within the scope of detecting, identifyingand/or measuring a touch event to detect, identify and/or measure hover(non-touch), contact and/or pressure.

Absent frame-phase synchronization, even in the absence of other stimuli(such as touch), phase may not remain stable from one frame to another.In an embodiment, if phase were to change from one frame to another(e.g., due to lack of synchronization) the information that could beextracted from changes in the phase may not reveal meaningfulinformation about a touch event. In an embodiment, synchronization ofphase for each frame (e.g., by methods discussed) in the absence ofother stimuli, phase remains stable frame-to-frame, and meaning can beextracted from frame-to-frame changes in phase.

It should be noted that while the frame-phase synchronized systemsprovided the basis for the present disclosure and the phase-relatedmeasurement and inventions described herein, it is not strictlynecessary to synchronize the frame-to-frame phase in order to havechanges in the phase may reveal meaningful information about a touchevent. Instead, in an embodiment, the receiver obtains information aboutthe phase of a signal as transmitted, and uses that information tonormalize the phase as received. Consider for discussion an exemplarysystem having the following operations repeated: transmission of rowsignals at a known phase begins; then the system waits a predeterminedtime for the row signals to charge the matrix; and then a frame of datais received from the columns. In an embodiment, provided that the “knownphase” is the same each time, the system is said to have frame-phasesynchronization because the where there are no touch events (or noise),the phase in each frame will remain constant. In an differentembodiment, where the “known phase” varies from instance to instance(e.g., shifts 10 degrees clockwise in each frame or randomly) the phasein each frame will also shift from frame to frame, making directframe-to-frame comparisons of phase data lack meaningful informationabout a touch event. Nonetheless, to the extent there is a known phaseat initiation and that known phase is known to the signal processor(which may be in the same integrated circuit as the transmitter), thatknown phase information can be used to normalize the received phase sothat frame-to-frame comparisons can be made. The point being thatalthough a frame-phase synchronization can support the present methodsand apparatus for phase detection of touch events, they are notnecessary. Instead, in an embodiment, what is needed is a knowledge ofthe transmit phase information during signal processing.

In an embodiment, heatmaps reflecting a measure of signal strength(often post-processed heatmaps, see e.g., U.S. Pat. No. 9,158,411entitled Fast Multi-Touch Post Processing) are often used in theidentification of touch events from a sensor. Elements in the heatmapgenerally reflect measurements corresponding to tixels or may beinterpolated values based on measurements corresponding to tixels. Seee.g., U.S. Pat. No. 9,158,411. In an embodiment, heatmaps reflectingchanges in a measure of signal strength are used in the identificationof touch events from a sensor. Heatmaps reflecting a measure of signalstrength or changes in a measure of signal strength will be collectivelyand individually referred to herein as Magnitude Heatmaps. In variousembodiments, identification of local maxima, or watershed transforms,are used with Magnitude Heatmap to identify or help identify touchevents.

In an embodiment, heatmaps reflecting signal phase or changes in signalphase (hereinafter, collectively and individually, Phase Heatmaps) maybe used to identify or help identify touch events. Phase Heatmaps differin kind from Magnitude Heatmaps as they do not reflect any measure ofsignal strength. Said differently, the Phase Heatmap will not change asa result of whether the received signal strength goes up or down as aresult of a touch event at a tixel. Instead, the Phase Heatmap reflectsa different phenomenon altogether. The Phase Heatmap is affected bychanges in the measured phase of the received signal. In an embodiment,the Phase Heatmap will change as a result a phase shift in the receivedsignal (clockwise or counterclockwise) as result of a touch event at atixel. Noise in the phase domain may also affect the Phase Heatmap. Itis believed that not all noise affecting signal strength measurementswill affect phase measurements, and not all noise affecting phasemeasurements will affect signal strength measurements. Thus, thecombination of a Phase Heatmap and a Magnitude Heatmap should produce alower noise result. In an embodiment, touch events identified on oneheatmap and but not present on the other are ignored. In an embodiment,potential touch events identified by being above one threshold but belowanother threshold on one heatmap are ignored unless they arecorroborated by potential touch events identified as being above athreshold on the other heatmap. It will be apparent to a person of skillin the art in view of this disclosure that there are many ways to usethe Phase Heatmap in combination with the Magnitude Heatmap.

In an embodiment, phase measurements are used to provide informationabout the status of the sensor, and change in phase measurements overtime are used to provide information about touch events. In anembodiment, a heatmap of phase measurements is generated for each frame.A heatmap is a way of visualizing (and storing) the phase data, itshould be understood that other ways of processing the phase data mayalso be used. Now, in addition to magnitude data taken from the receivedsignals, or instead of the magnitude data, phase data can be used inorder to provide information about a touch event.

For example, in an embodiment, a Phase Heatmap can be used in order tocheck the accuracy of a Magnitude Heatmap. The Phase Heatmap and theMagnitude Heatmap can be compared in order to verify the changes thatare occurring due to touch events. Discrepancies between the twoheatmaps can be disregarded or alternatively handled, e.g., with touchevents or conditions where the magnitude-related data may be morereliable or less reliable than the phase-related data.

In an embodiment, the Phase Heatmap can be used to complement theMagnitude Heatmap. The Phase Heatmap can provide data that gives moreinsight into the touch event when used to complement the MagnitudeHeatmap.

In an embodiment, the Phase Heatmap may be used or preferred forselected touch events, for example, for hover or for determining anapproach. The Phase Heatmap may provide additional insight regardingtouch events at far distances.

Exploration of the use of phase-related data led to potentialapplications of phase-related data measurements. In an illustrativeembodiment, a tixel comprises a transmit antenna that is used totransmit two different frequency-orthogonal signals, one at a relativelylow frequency and the other at a relatively high frequency. While thereis noise and jitter in all measurements, it has been observed thatphase-related data for the lower frequency signal appears to have lessjitter for more distant hover-type touch events, while themagnitude-related data for the higher frequency signal appears to haveless jitter for nearer, touch-type touch events.

In an embodiment, multiple (two or more) frequency-orthogonal signalsare used for one or more tixels. In an embodiment, a Magnitude Heatmapis generated for the high frequency signals and a Phase Heatmap isgenerated for the low frequency signals, and both heatmaps are used todetermine touch (including hover). In an embodiment, a Magnitude and aPhase Heatmap are generated for both the high and low frequency signals,in determining touch, the Magnitude Heatmap is weighted heavier withrespect to the high frequency signal and the Phase Heatmap is weightedheavier with respect to the low frequency signal. In an embodiment, aMagnitude and a Phase Heatmap are generated for both the high and lowfrequency signals, in determining touch, a Magnitude and a Phase Heatmapare generated for both the high and low frequency signals, indetermining touch, and both heatmaps are used in determining touch.

Stated differently, the use of phase-related data is coupled with anobservation that (other things being equal) low frequency signalsappeared to have tixels that are affected by touch further away from thesurface than signals with higher frequencies. A further observation isthat the phase-related data may be more relevant for some frequenciesover others. In other words, the phase data for the higher frequencies,i.e., the frequencies with further extending fields, may be morereliable and/or consistent than the magnitude-related data at distancesfurther away from the touch surface.

Referring back to FIG. 1, an embodiment of a sensor 100 is shown. Thesensor has a row conductor 201 and a column conductor 301 that cross(when viewed in plan), but are separated from one-other by air or adielectric material (not shown) at tixel 401. In an embodiment, aplurality of orthogonal signals are transmitted over the row conductor201. In an embodiment, the signals are frequequency orthogonal. Theplurality of signals transmitted over the row conductor 201 interactwith the column conductor 301 at tixel 401 where the two are proximate(e.g., where they cross). While the tixel 401 is shown as being at alocation where the row conductor 201 and the column conductor 301 cross,it should be understood that this is for illustrative purposes only andthat the tixel 401 may be at any location where there is couplingbetween the row conductor 201 and the column conductor 301 (or similarstructures like antennas, plates or dots). Although only one row and onecolumn are shown, many of each may exist forming a grid.

In an embodiment, a receiver (not shown) receives and digitizes signalson column conductor 301. In an embodiment, the signals are digitized fora period of time, and the digitized signals are sent to a signalprocessor (also not shown) where they are processed to determine ameasure for each signal transmitted over the row conductor 201. Asdiscussed above, digitization may take place at any speed. In anembodiment, at least 1 MHz. In an embodiment, any time window(integration period) may be used for sampling. In an embodiment, 4096samples are taken a 4 MHz (approximately 1 millisecond). The transmittedorthogonal frequencies should have a spacing between each signal that isnot less than the reciprocal of the integration period. In anembodiment, the transmitted orthogonal frequencies have a spacingbetween each signal that is the reciprocal of the integration period.For a frequency spacing of at least 1 Khz is used for an integrationperiod of 1 ms.

In an embodiment, the digitized signals are processed by a DFT (whichcould be an FFT) and an I and Q component are determined for each signaltransmitted over the row conductor 201. In an embodiment, the conductorsor antennas on the sensor 100 are operatively connected to transmittersand receivers in an integrated circuit capable of transmitting andreceiving the required signals. In an embodiment, the integrated circuitis also capable of acting as the signal processor. In an embodiment, theintegrated circuit contains a communications channel to a GPU where someor all of the signal processing is done. In an embodiment, thecommunications channel comprises SPI, or multi I/O SPI such as quad-SPI.

In an embodiment, the transmitters and receivers are each operativelyconnected to a different integrated circuit capable of transmitting andreceiving the required signals, respectively. In an embodiment, thetransmitters and receivers for all or any combination of patterns may beoperatively connected to a group of integrated circuits, each capable oftransmitting and receiving the required signals, and together sharinginformation necessary to such multiple IC configurations. In anembodiment, where the capacity of the integrated circuit (i.e., thenumber of transmit and receive channels) and the requirements of thepatterns (i.e., the number of transmit and receive channels) permit, allof the transmitters and receivers for all of the multiple patterns usedby a controller are operated by a common integrated circuit, or by agroup of integrated circuits that have communications therebetween. Inan embodiment, where the number of transmit or receive channels requiresthe use of multiple integrated circuits, a hub is used to aggregate theinformation from each circuit which is combined and processed in aseparate system. In an embodiment, the separate system comprises a GPUand software for signal processing.

In an embodiment, a signal is transmitted on the transmitter row 201. Inan embodiment, more than one signal is transmitted on the transmitterrow 201 with each of the signals transmitted on the transmitter row 201orthogonal to each other. In an embodiment, more than one signal may betransmitted on the transmitter row 201 with each of the signalstransmitted on the transmitter row 201 being frequency orthogonal andrange from a lowest to highest frequency.

In an embodiment, more than one signal may be transmitted on thetransmitter row 201 with each of the signals transmitted on thetransmitter row 201 being frequency orthogonal and at least 10 kHz apartin frequency. In an embodiment, more than one signal may be transmittedon the transmitter row 201, with each of the signals transmitted on thetransmitter row 201 being frequency orthogonal and between 10-50 kHzapart in frequency. In an embodiment, more than one signal may betransmitted on the transmitter row 201 with each of the signalstransmitted on the transmitter row 201 being an integer frequency thatis frequency orthogonal to and at least 1 kHz apart from the otherinteger frequencies. In an embodiment, more than one signal may betransmitted on the transmitter row 201 with each of the signalstransmitted on the transmitter row 201 being an integer frequency thatis frequency orthogonal to and at least 1 kHz, but not more than 1 MHzapart from the other integer frequencies.

When two frequency-orthogonal signals are being transmitted, one of thetransmitted signals is deemed high frequency and the other is deemed lowfrequency. In an embodiment, a low frequency of 200 kHz and a highfrequency of 399 kHz, thus keeping the low and high frequency within oneoctave. In an embodiment, a low frequency of 50 kHz and a high frequencyof 199 kHz. In an embodiment, a low frequency of 100 kHz and a highfrequency of 1.5 MHz.

In an embodiment, when three frequencies are being transmitted, one ofthe transmitted frequencies is deemed the high frequency, one deemed thelow frequency and a third is deemed a mid frequency that falls betweenthe high and low frequencies. For example, the low frequency may be 50kHz and the high frequency may be 100 kHz, while a third frequency maybe 75 kHz. In an embodiment, more than three frequencies aretransmitted.

In an embodiment, when more than two frequencies are being transmitted,one of the transmitted frequencies may be considered the high frequency,one of the transmitted frequencies may be considered the low frequencyand the other potential plurality of frequencies may fall within afrequency range near the high and low frequencies. For example, the lowfrequency may be 50 kHz and the high frequency may be 100 kHz, and twoother frequencies may fall within 10 kHz of these values. For examplethe other two frequencies may be 55 kHz and 95 kHz. Providing additionalorthogonal frequencies within a certain range of the highest and lowestfrequencies can provide additional information regarding the phaseshift.

In an embodiment, multiple transmit conductors or antennas are each usedto transmit multiple orthogonal frequencies. In an illustrativeembodiment, 4096 samples are taken a 4.096 MHz (to make the math easyfor the illustration), and the transmitted orthogonal frequencies have aspacing between each signal that is the reciprocal of the integrationperiod. The following tables provides an illustrative example, the firstof the use of a high and a low frequency, within an octave, for fivetransmit antennas:

Low High TX1 50 kHz 90 kHz TX2 51 kHz 91 kHz TX3 52 kHz 92 kHz TX4 53kHz 93 kHz TX5 54 kHz 94 kHzThe following table provides an illustrative example of the use of threefrequencies, within an octave, for five transmit antennas:

Low Third High TX1 200 kHz 250 kHz 350 kHz TX2 201 kHz 251 kHz 351 kHzTX3 202 kHz 252 kHz 352 kHz TX4 203 kHz 253 kHz 353 kHz TX5 204 kHz 254kHz 354 kHzThe following table provides an illustrative example of the use of threefrequencies for five transmit antennas:

Low Third High TX1 250 kHz 750 kHz 1.204 MHz TX2 251 kHz 751 kHz 1.203MHz TX3 252 kHz 752 kHz 1.202 MHz TX4 253 kHz 753 kHz 1.201 MHz TX5 254kHz 754 kHz 1.200 MHzIn each example, the transmitted orthogonal frequencies have a 1 kHzspacing between each signal.

In an embodiment, the field generated by a low frequency signal and thefield is generated by a higher frequency signal differ in that the fieldassociated with the low frequency signal is believed to extend furtherfrom the tixel than the field created with the higher frequency. In anembodiment, a height above a touch surface corresponds to a distancefrom a tixel (such height sometimes referred to herein as the Z-axis,where X- and Y-refer to translation across the touch surface).

It has been suggested by observation that, to some degree:

(i) at a relatively large Z-axis height,

-   -   (a) a tixel's low-frequency interactions appear smoother when        measured in the phase domain than in the magnitude domain,    -   (b) a tixel's low-frequency interactions in both the magnitude        and phase domain appear smoother than when compared to the        tixel's high-frequency interaction; and

(i) at a relatively small Z-axis height,

-   -   (a) a tixel's high-frequency interactions appear smoother when        measured in the magnitude domain than in the phase domain,    -   (b) a tixel's high-frequency interactions in both the magnitude        and phase domain appear smoother than when compared to the        tixel's low-frequency interaction.

In an embodiment, the measurements made by a sensor with respect tovarious frequencies and in magnitude and phase may be weighted orotherwise applied in an uneven manner. In an embodiment having a highand low frequency and both phase and magnitude measurements, as a fingerfirst comes into interacting proximity with a tixel, one weighting isapplied to understand the touch event; then as the finger moves closerto the tixel, another weighting is applied to understand the touchevent; and finally, as the finger makes contact and begins exertingpressure at the tixel, yet another weighting is applied to understandthe touch event. In an embodiment having a high a low frequency and bothphase and magnitude measurements, as a finger first comes intointeracting proximity with a tixel, one weighting is applied tounderstand the touch event (e.g., low frequency phase information ismore heavily weighted); then as the finger moves closer to the tixel,another weighting is applied to understand the touch event (e.g., abalance between low frequency and high frequency magnitude and phaseinformation); and finally, as the finger makes contact and beginsexerting pressure at the tixel, yet another weighting is applied tounderstand the touch event (e.g., high frequency magnitude informationis more heavily weighted). It will be apparent to a person of skill inthe art in view of this disclosure that there will be many differentapplication-specific or application-preferred manners to use thetouch-event related data from multiple frequencies and from themagnitude and phase domains, to interpret the touch events causing thechanges on a sensor, all of which are intended to fall within the scopeand spirit of this disclosure. Experimentation with particularconfigurations to determine adequate or preferred combinations of theuse of this data is within the skill in the art in view of thisdisclosure and its discovery of the principles and concepts describedherein. In sum, the relative sensitivities of the low frequency signalsand the high frequency signals with respect to the magnitudes and phasescan provide more information regarding a touch event. The additionalinformation can provide a clearer and more predictable, i.e., lessjittery or random, interpretation of movements associated with the touchevent.

In an embodiment, the phase information of a touch event in the lowfrequency range can provide a clearer view of what is occurring with atouch event high on the Z-axis. The magnitude of a touch event in thehigh frequency range can provide a clearer view of what is occurringwith a touch event low on the Z-axis, when compared with events high onthe Z-axis. The magnitude data low on the Z-axis and the phase data highon Z-axis can provide a better overall view of a touch event across alarger range of the Z-axis.

In an embodiment, a plurality of frequencies may be used which willproduce multiple levels of field sensitivity along the Z-axis. Both themagnitude and phase information taken from a touch event may be combinedto create a composite view of a touch event. In an embodiment, magnitudeinformation may only be taken from low on the Z-axis while phaseinformation may only be taken from high on the Z-axis. In an embodiment,magnitude information may be taken from both low and high on the Z-axis,while phase information may be taken only from high on the Z-axis. In anembodiment magnitude and phase information may be taken from both highand low on the Z-axis.

In an embodiment, keyboards may be made that are able to detect touchevents using both phase and magnitude data as discussed above. The useof both the phase and magnitude data may provide a better range ofinteractivity for a user of a keyboard. It should be understood thatwhile keyboards were mentioned above, the discoveries, methods andapparatus discussed herein are more generally applicable, and can beused, for example, in connection with sensors used in touchpads,handheld controllers, automotive cockpit applications (steering wheel,seat, console), musical instruments, motorcycle interfaces (handlebars,seats), transparent displays, detection of active and passive objects(e.g., stylus), gaming and sporting objects (e.g., bats, balls, grips),and for numerous other sensor-based applications.

Displacement Vector

At hover and distances high on the z-axis, the magnitude and phase datamay not be significantly above baseline variance. This may make themagnitude or phase data, or both, less reliable for the detection of farhover and proximity (even longer) touch events—i.e., touch events farfrom the tixel where its measurements are being taken.

Another observation made as a consequence of experiments with phaseframe synchronized systems is that a touch delta (vector) can bemeasured and used to describe touch interaction. A touch delta can beinexpensively determined (computationally) from successive IQmeasurements.

In an embodiment, a baseline touch delta is calculated by averaging eachof a plurality of I and Q components during baseline conditions (e.g.,no detected touch). In an embodiment, the baseline touch delta can beupdated (e.g., re-calculated) periodically or continuously to accountfor baseline changes. Baseline changes may be environmental orotherwise.

The baseline can be calculated using the real and imaginary componentsof a discrete Fourier transform, e.g., FFT. For example, the baselinemay be calculated by using 100 samples in baseline conditions in orderto obtain an average real component and an average imaginary component.This will then result in an average magnitude component such as shown inFIG. 4. More specifically, FIG. 4 illustrates a vector (magnitude)representing an average of real (I) and imaginary (Q) components for aplurality of samples taken during baseline conditions.

The change in magnitude and phase angle from frame to frame can be usedto calculate a displacement vector such as shown in FIG. 5. In anembodiment, the displacement vector can be inexpensively calculated(computationally) by subtracting the I and Q components of the baselinefrom the I and Q components of the measured signal.

Certain touch deltas can be ignored, e.g., not treated as touch-relateddata, because of their characteristics. In an embodiment, changes inmagnitude (i.e., touch delta magnitude) below a certain threshold areignored. In an embodiment, touch delta phase angles that are notconsistent with rotation due to touch objects are ignored. In anembodiment, in a given system where it has been observed that a touchdelta phase angles resulting from touch events are counterclockwisewithin a given range (around a standard IQ 2D axis), variations from thetouch-event related counterclockwise direction range may be disregarded,e.g., clockwise touch delta phase angles can be ignored. In anembodiment, both touch delta magnitude and phase angle ranges are usedas a basis to reject (ignore) data from the sensor.

In an embodiment, a number of displacement vectors may be collected andused to create a heatmap of the displacement vector magnitudes. In anembodiment, a displacement vector heatmap can be used as a check on theaccuracy of the Magnitude Heatmap. In an embodiment, the displacementvector heatmap can be used to complement the Magnitude Heatmap. In anembodiment, the displacement vector heatmap may be used for only aselect few touch events, for example, for hover or for determining anapproach. In an embodiment, the displacement vector heatmap and thePhase Heatmap can be used as a check on the accuracy of the MagnitudeHeatmap. In an embodiment, the vector displacement heatmap and the PhaseHeatmap can be used to complement the Magnitude Heatmap. In anembodiment, the displacement vector heat map and the Phase Heatmap maybe used for only a select few touch events, for example, for hover orfor determining an approach. In an embodiment, the Phase Heatmap, thedisplacement vector heatmap and the Magnitude Heatmap can be usedtogether to determine/validate/reject touch events.

In an embodiment, the changes in the displacement may be used to providea check of touch data at a distance further from a touch surface thaneither phase data or magnitude data can provide by themselves. In anembodiment, the displacement vectors are used to reinforce existingtouch data. In an embodiment, the displacement vectors are used toimprove the likelihood that frame measurements are only susceptible toactual touch objects.

With the use of three representations of touch event data; magnitude,phase and vector displacement, a more complete view of a touch event andthe surrounding environment is possible.

The several embodiments discussed above illustrate a variety of systemsand methods for phase measurement, but are not intended to limit thescope of the claims. Other systems and methods of using phasemeasurement to improve touch data will become apparent to persons ofskill in the art in view of this disclosure, and are thus includedwithin the scope of this disclosure.

It is understood that each block of the block diagrams or operationalillustrations, and combinations of blocks in the block diagrams oroperational illustrations, when used or discussed above, may beimplemented by means of analog or digital hardware and computer programinstructions. Computer program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, ASIC,or other programmable data processing apparatus, such that theinstructions, which execute via a processor of a computer or otherprogrammable data processing apparatus, implements the functions/actsspecified in the block diagrams or operational block or blocks.

Except as expressly limited by the discussion above, in some alternateimplementations, the functions/acts noted in blocks may occur out of theorder noted in any operational illustrations. For example, the order ofexecution if blocks shown in succession may in fact be executedconcurrently or substantially concurrently or, where practical, anyblocks may be executed in a different order with respect to the others,depending upon the functionality/acts involved.

While the invention has been particularly shown and described withreference to a preferred embodiment thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention.

The invention claimed is:
 1. A sensing apparatus, comprising: aplurality of antennas comprising a first antenna group and a secondantenna group, the plurality of antennas positioned such that a touchevent in proximity to the sensing apparatus causes a change in couplingbetween at least one of the antenna in the first antenna group and oneof the antenna in the second antenna group; a signal generatorconductively connected to each of the first antenna group, the signalgenerator adapted to generate at least one frequency signal on each ofthe first antenna group, each of the at least one frequency signalshaving a transmit phase during each of a plurality of sequentialintegration periods; a signal receiver conductively connected to each ofthe second antenna group, the signal receiver adapted to take a sequenceof digital samples of signals on each of the second antenna group duringthe plurality of sequential integration periods; a signal processingsystem operatively connected to the signal receiver, the signalprocessing system being adapted to: for each of the plurality ofsequential integration periods, determine a receive phase correspondingto each of a plurality of distinct signals based on the sequence ofdigital samples of signals taken during an integration period; andcreate a heatmap reflecting changes between the transmit phase and thereceive phase.
 2. The sensing apparatus of claim 1, wherein arelationship between the transmit phase the receive phase is used tocreate the heatmap.
 3. The sensing apparatus of claim 2, wherein therelationship is determined by subtracting a known phase variation of theplurality of distinct signals.
 4. The sensing apparatus of claim 2,wherein the relationship is determined by having the signal generatoruse a known transmit phase.
 5. The sensing apparatus of claim 2, whereintiming of the integration period is moved to ensure use of a knowntransmit phase.
 6. The sensing apparatus of claim 1, wherein onlyintegration periods having known transmit phases are used.
 7. Thesensing apparatus of claim 1, wherein the signal processing system isfurther adapted to determine a magnitude of at least one of theplurality of distinct signals to assist in creating the heat map.
 8. Thesensing apparatus of claim 1, wherein the signal processing system isfurther adapted to determine a phase shift of at least one of theplurality of distinct signals to assist in creating the heat map.